Introduction

The market of APS-C format ultra-wide zoom lenses is very crowded. A brief look into the price lists reveals no less than 7 competing lenses in Canon EF mount (2x Tokina, 3x Sigma, 1x Tamron, 1x Canon) as of the time of this review which simply shows that this is a customer hot spot. And we have to add at least one further full format lens here - the Sigma AF 12-24mm f/4.5-5.6 HSM DG II which is, of course, also usable on APS-C cameras. It is basically the only full format ultra-wide zoom lens that it still capable of delivering a very wide field-of-view on the crop format as well (equivalent to a Tokina AF 12-24mm f/4 AT-Pro DX II for instance). As such it is an obvious candidate for users who plan to migrate from an APS-C to a full format camera in the foreseeable future. You have to pay a little more for the privilege, of course - bigger glass doesn't simply come for free. A couple of years ago we already tested its predecessor with reasonably good but not great results. Let's see whether the completely new design of the mk II can make a difference here. The use of Sigma's new FLD glass is promising for sure as we've already seen in the Sigma AF 8-15mm f/4.5-5.6 HSM DC in one of our recent tests.

The build quality of the Sigma lens is very high thanks to a tightly assembled combination of plastic and metal parts based on a metal mount. The zoom and focus control rings feel slightly stiff but therefore also very precise. The physical length of the lens remains constant at all zoom and focus settings although the inner lens tube moves a little. A non-detachable petal-shaped lens hood does not only help to combat sided light but it also protects the vulnerable "bulb-like" front element from scratches. The two-part lens cap can be slipped over the metal lens hood. The front cap can be removed and allows to mount a filter to the base unit of the cap. However, this makes rather limited sense because even the base unit will already produce vignetting at the widest zoom settings.

Typical for most Sigma lenses, the AF mechanism relies on a "Hypersonic Motor" (HSM) which is both fast and nearly noiseless. The AF precision of the tested sample was just soso which may not even be a limitation of the lens but rather the camera which suggested near-infinity focus settings most of the time. This is not really desirable anyway though because you are wasting lots of depth-of-field potential but more on this later.